The present invention relates to molded elastomeric products, and more particularly to orienting molded elastomeric products.
Molded elastomeric products have a wide variety of applications. To enhance the performance of these products in certain applications, U.S. Patent Publication No. 2005/0279591 A1 teaches that it may be beneficial to orient the product, which involves stretching and releasing the product to align the crystalline structure of the plastic in a particular direction, or, in some cases, multiple directions. Orientation of a product will alter its material properties, including its stiffness and/or support characteristics. Typically, the product will be oriented to such a degree that the oriented product has materially different material characteristics in the oriented direction than in other directions. The amount of stretch required to obtain the desired material characteristics will vary from application to application, but in most applications, the desired orientation will occur when the product is stretched to roughly two times its original dimension. Because the product is stretched beyond its elastic limit, it recovers to an intermediate dimension that is deformed from its original length. This deformation is non-recoverable, permanent deformation. As a result of this orientation and non-recoverable deformation, a degree of permanent deformation is removed from the oriented product, such that when subsequent stresses within the desired normal operating load are applied to the oriented product, the product resists permanent deformation over time (i.e. creep).
Although the product may be oriented by stretching using a variety of methods and under a variety of conditions, a number of parameters may be controlled to provide the product with a desired amount of orientation. For example, a slow, controlled stretch aids in maintaining a uniform orientation across the membrane. The orientation may also be cyclic, in which the product is oriented by stretching it to a first distance, then relaxed to a second, intermediate distance, and then stretched to a second distance greater than the first. The sequence may be repeated as many times as necessary to achieve the desired orientation. A cyclic orientation process helps compensate for any irregularities within the material to provide a uniform stretch, because areas of greater or lesser stretch will even out after multiple cycles. Thus, the support characteristics of the molded product are highly adjustable by the orientation process, thereby permitting the molded elastomeric product to be tailored to a variety of different applications.
After the product is released from the final stretch of the orientation process, the product recovers to an equilibrium position. Manufacturing processes involving orientation commonly include a recovery station where the oriented products sit until they have completely recovered to the equilibrium position, at which the product is ready to be put into its final application. Unfortunately, the recovery process adds time to the manufacturing cycle, and, in some applications, it may be difficult to manipulate the product into its final application once the product has recovered.